The present invention relates to resin coated photographic support papers with improved yellow dark stability.
A considerable amount of the photographic base paper used in the world is resin coated. It is used as an image receiving support for prints produced by a number of different photographic processing systems. Imaging paper, particularly photographic imaging paper, requires materials in the image support that provide long term survivability and stability during both display and storage. These properties are most desirable and have significant commercial value.
The resin is normally a polyolefin, for example polyethylene, and the resulting resin coated base papers are substantially impervious to water and photographic chemical processing solutions. Resin coated base papers therefore require less drying time and consequently can be processed more quickly. In addition, resin coated base papers use less processing chemicals and are substantially free from distortion. This is of special concern to prints produced from the negative-positive process, especially color prints, which generally require longer periods of immersion in the processing solutions than is the case with black and white printing paper.
When imaging supports are subject to variations in ambient conditions over long periods of time the image containing and face side resin layers tend to deteriorate into a mass of cracks which are aesthetically undesirable and which, in extreme cases, extend over the entire print completely destroying the image. All polymers are inherently prone to chemical degradation that leads to loss of mechanical properties. The polymers undergo thermal degradation during processing such as extrusion of thin films, and photooxidative degradation with long term exposure to light. Titanium dioxide catalyzes and accelerates both thermal and photooxidative degradation. In the art of resin coating imaging papers, the melt polymers are extruded at high temperatures and are also subjected to high shear forces. These conditions may degrade the polymer, resulting in discoloration and charring, formation of polymer slugs or xe2x80x9cgelsxe2x80x9d, and formation of lines and streaks in the extruded film from degraded material deposits on die surfaces. Also, thermally degraded polymer is less robust than nondegraded polymer for long term stability, and may thereby shorten the life of the print.
Hindered phenolic antioxidants are commonly used alone or in combination with secondary antioxidants to stabilize polymers during melt processing, but provide little protection from long term photooxidation. The phenolic type antioxidants also decrease the ability of the resin to adhere to the paper during the high speed extrusion process. They are also responsible for some forms of oxidative atmospheric gas yellowing in prints stored in the dark. This undesirable color may develop on the print or around the print edges with archival keeping, and has been attributed to colored oxidation products of phenolic antioxidants that are formed in the dark in the presence of white pigments, such as titanium dioxide.
U.S. Pat. No. 4,582,785 suggests using a polymeric hindered amines with greater than 2500 molecular weight as the sole stabilizer, which, when added to polyethylene coated photographic papers, can improve their photostability. In this patent, a polymeric hindered amine is claimed as the sole stabilizer for both thermal processing and light stability in a single layer of a polymeric material, polyethylene. The adhesion of the polymeric hindered amine containing resin to the paper is poor. Furthermore, it is desirable to make imaging elements from polymers other than polyethylene or other than polymers in combination with polyethylene. The use of such materials as polyester and or polypropylene may add improved stability and durability to the element, as well as improved gloss and sheen.
U.S. Pat. No. 4,562,145 suggests a photographic base paper in which the resin coating contains a phosphonate stabilizer to substantially inhibit cracking. Moreover, these stabilizers can conveniently be admixed with the resin prior to extrusion coating of the resin on to the support without any significant detriment to the adhesion and quality requirements of the resin coating and may contain other ingredients, such as light stabilizers, which are hindered amines. Preferred monomeric hindered amine light stabilizer are bis{2,2,6,6-tetramethyl-4-piperidinyl}sebacate (sold by Ciba-Geigy under the trade name of xe2x80x9cTinuvin(copyright) 770xe2x80x9d), xe2x80x9cTinuvin(copyright) 622xe2x80x9d and xe2x80x9cChimassorb(copyright) 944xe2x80x9d (abbreviated herein as CHIM 944) by Ciba-Geigy and Chimosa respectively.
There remains a need to provide an imaging support that contains pigments that are extrusion processable at low temperatures and high speeds without drying the paper, creating gels, or creating photoactive products which will fog the photographic emulsion. In addition, the imaging support must have exceptional long term resistance to degradation and embrittlement when exposed to light and other environmental stresses, while providing an imaging support that has exceptional dark stability and prevents discoloration during dark keeping.
There remains a need for an imaging element which, when stored for extended times in dark storage conditions, experiences improvement in the dark keeping of the yellow dye, thus, extending the useful life of the color photograph yellow image dyes of the imaging element.
The present invention relates to an imaged element comprising at least one imaged layer comprising at least one yellow dye and a support, wherein the support comprises at least one face side resin layer comprising a material capable of improving the yellow dark stability of the imaged element, wherein the material has the formula: 
The present invention includes several advantages, not all of which are incorporated in a single embodiment. One advantage provided by the present invention is improved properties after aging. It is a further advantage to provide polyolefin materials that may successfully be extruded at lower temperatures and high speeds onto paper and have improved adhesion of polyolefin layers.